iio: hid-sensor-temperature: Fix issues of timestamp channel

This patch fixes 2 issues of timestamp channel:
1. This patch ensures that there is sufficient space and correct
alignment for the timestamp.
2. Correct the timestamp channel scan index.

Fixes: 59d0f2da

 ("iio: hid: Add temperature sensor support")
Signed-off-by: Ye Xiang <xiang.ye@intel.com>
Cc: <Stable@vger.kernel.org>
Link: https://lore.kernel.org/r/20210303063615.12130-4-xiang.ye@intel.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>